The present invention relates generally to an elastic band heat activation system, including a method and apparatus for activating a heat-sensitive thermal film attached to an edge of a body of an article to form an elastic band along the edge of the article.
For example, the article may be an elasticized disposable headband or sweatband, a hospital surgical gown, a surgical hat, a pair of surgical booties, or a disposable incontinence garment, such as a disposable diaper with the elastic band formed thereon being a waistband. For the purposes of illustration, the finished product discussed herein will be a disposable diaper with an elastic waistband. It should be clear that the objects, techniques, features and advantages of the present invention may be applied to any such article to form an elastic band along the edge of the article.
Other activation systems have been used to activate a heat-shrinkable film located in a waistband portion of a disposable diaper to promote a high production rate without excessively heating the remaining portions of the diaper. These earlier systems included a continuous production apparatus having an enclosed heating zone in which hot air is blown toward the waistband portion of a plurality of disposable diapers, each having an elastic heat-shrinkable film attached thereto. The diapers are transported through the enclosed heating one on an endless conveyor. To increase the energy efficiency of the system, the hot air is recycled. After heating the waistband, the diapers are allowed to cool to ambient temperature using the natural convection currents within a room where the diapers are located.
One known apparatus has an inverted U-shaped heating shroud through which the diapers are conveyed. The shroud has a plurality of jet openings for directing hot air jets toward the waistband portions of the diaper. The shroud may be automatically raised and lowered relative to the path of travel of the diapers to regulate the heat applied thereto. A greater volume of air is drawn off the diapers than the volume of hot air supplied to the waistband portions, so cooler ambient air is drawn over the remaining portions of the diapers and the components of the apparatus and extracted with the hot air.
In these known systems, the disposable diaper folded along a transverse axis, so that the front waistband portion lies adjacent to the back waistband portion. The diapers are then transported in this state with the front and back waistband portions adjacent one another and directed toward the hot air source. Disadvantageously, the close proximity of the front and back waistband portions often prevents the hot air from entering the region of the diaper between the front and back waistband portions. This often results in non-uniform heating of the heat-shrinkable film which may cause improper shrinkage of the elastic, resulting in an inconsistent product.
After heating in these known systems, the gradual cooling to ambient temperature does not provide a controlled duration of heating. This uncontrolled heating duration may disadvantageously produce inconsistencies in the final finished products. Therefore, the earlier known systems often produce inconsistent products on a given assembly line, increasing the quality control problems for the article manufacturer, which in turn drives up the product cost.
Thus, a need exists for an improved elastic band heat activation system, including a method and apparatus, for activating a heat-sensitive thermal film attached to an edge of a body of an article to form an elastic band along the edge of the article, which is not susceptible to the above limitations and disadvantages.